[meteorite-list] Etching solution
From: MexicoDoug <mexicodoug_at_meteoritecentral.com>
Date: Sat, 28 Jan 2012 00:18:27 -0500 (EST) Message-ID: <8CEAB936687B37C-1584-A49E_at_webmail-m151.sysops.aol.com> Sure Mark, now that you dropped the respectful line completely, I don't appreciate being baited. "One last item - you may want to calculate the percent composition of the 3 molar (normal) solution you are recommending and compare the figure to Bretherick's data for instability." What a complete fool you've made of me taking you seriously and looking by looking up great references + doing a bit of original research into alcohol selection for nital all becasue you decided to be a nitpick. You can say you aren't confused but that doesn't make it it true. You actually offered little more than the above quoted comment in dispute, called yourself a certified expert, provided an admitted dubious link to wikipedia, made me work to provide you references which I did, and then said to be careful with chemicals which had been repeated by all before you joined the thread (well that is worthwhile repeating). So whatever it is you stand by, good job. Doug -----Original Message----- From: Mark Grossman <markig at westnet.com> To: Meteorite-list <Meteorite-list at meteoritecentral.com>; MexicoDoug <mexicodoug at aim.com> Sent: Fri, Jan 27, 2012 11:13 pm Subject: Re: [meteorite-list] Etching solution Hi Doug, I didn't confuse anything - I'll leave that job up to you - and I'll stand by what I stated before. Best, Mark ----- Original Message ----- From: "MexicoDoug" <mexicodoug at aim.com> To: <markig at westnet.com>; <Meteorite-list at meteoritecentral.com> Sent: Friday, January 27, 2012 10:18 PM Subject: Re: [meteorite-list] Etching solution Hi Mark Wow, with the due respect, all that experience under your belt, I really am surprised you confused the difference between threshold toxicity level and toxic activity! But it illustrates the dangers of misinterpretion that are part of life in these sorts of postins when nobody gets exactly right what the other guy says. OK, I'll work on this I feel a response is required (and I reall didn't want to, please excuse my tone but other things happening around me have me very stressed and I am sure the tone is suffering), as you described 'good intent' to clear up what you interpret as too casual. I don't like that label at all, innocent or even if true. Let's fix your easy objections right here and now: I suspect the mechanism of explosive reaction with isopropyl alcohol is unique vs. the others is becasue it reacts with the nitric acid to form the unstable explosive trinitromethane (TNM), the methane analog of trinitrotoluene (TNT). This is a favored reaction when mixing these two compounds, not some pie in the sky idea. Some fireworks are commercially made by mixing isopropanol with nitric and it probably was in the Anarchist's Cookbook, which unfortunately I dropped acid on many years ago and destroyed by mistake. There - likely mechanism hypothesis. Explains violence in explosion. I don't think you'll find that on the MSDS ;-) but it ouigh to be. please don't make me work anymore ;-( Also, so as not to be accused of being casual here is a reference for Isopropyl alcohol being too explosive for using in nital. As I mentioned it is anecdotal even if the world expert of the time said it and it is mindlessly repeated today, but if you combine that with the mechanism we have a workingtheory that makes sense: ANDERSON, Roy L.: A brief discussion of safety in the metallography laboratory, The Microscope, 14, 180 (1964) That author was the guy in charge of saftely I believe at Westinghouse, which was the American pride and joy and gold standard for lab safety. It discusses spontaneous explosion and a death or two when preparing nital with isopropanol and that is good enough for me. Please don't read this as making ethanol any safer; obviosuly it's not but that's a horse of another color. Just becasue something is preferred doesn't mean it is completely safe and that is what I meant by the "devil you know" or at least that the industry knows. Now, I've provided you not only with the two references you've asked for, but a proposed mechanism as well. As for my 3 N use of nitric acid, your implication is on the wrong path in my case if you suggesting, that it is in the danger zone? Nontheless good to clarify it. This concentration may scrape the lower danger limits of flammability when preparing nital but really it is quite infinitesimal amounts during dilution and mixing with insufficient mass to present any problem, I am quite comfortanle with it. In a well vented open system it presents no problem whatsoever; however if some freak incident happens as is always a real possibility, for the risk averse, they should not do this. Nor anything that involves any risk, not even breath in the extreme. What I think you missed, is that straight 3 N HNO3 is perfect for a reasonably fast etch, though certainly half that concentration can be used. But I hope I suggested to use it WITHOUT the alcohol specifically to avoid any alcohol related problems - it just can't getany simplier to etch in relative safety and get the benefit of a nitric acid etch. Furthermore, if preparing nital with alcohol, unless I've made a gross typo somewhere, let me remind you that when you mix the aqueous 3 N HNO3 with the alcohol to make Nital, the concentration of the acid is proportionally reduced by the greater volume of the resulting mixture. Thus a 50:50 mixture for example of 3 N nitric acid with the alcohol will lower the concentration into safe ranges. The whole slant of my posts were to NOT use concentrated nitric acid for anything since it is completely unnecessary for beginners. I think that wraps that up. Other than to say if someone is not confident based on understanding what they are doing, better not to do it at all. Accidents happen, but that's what hoods, goggles and face masks, and small amounts are for... this is not something to store in bottles making big batches, but rather to minimize reagent use. What is not written in the 'safety manual', is that the vast majority of accidents happen when ethanol is used with concentrated nitric acid, not the rather dilute form. The drawback of my method is it contains water from the dilute acid, but I'll just repeat that I think water is getting a bum wrap here. If you use alcohol in the rinse / dry stage, really, who cares. Plus as I mentioned water is part of the FeCl3 etching process always. I don't value the benefit of going anhydrous during etching, that is what drying is for, or better yet, get a dessicator or combo oven. Finally I do recognize that Mark is more concerned with preventing someone from taking information from these posts and running off half-cocked to blow their head off. That's reasonable! That is a very good caution to make and I applaud it. The only difference I may have is that I like to have a place to get this sort of information, so why not consider this exactly as presented, a start for someone to learn more and for all to discuss and improve. My thought, by the time anyone goes through all of this, if they were thinking of exoperimenting, they will be infinitely better off than the guy who just pours stuff haphhazardly together without rhyme or reason hoping to strike it lucky. Kindest wishes Doug In the spirit of demystifying all this terrible cloak and dagger stuff surrounding the etching process! -----Original Message----- From: Mark Grossman <markig at westnet.com> To: Meteorite-list <Meteorite-list at meteoritecentral.com>; MexicoDoug <mexicodoug at aim.com> Sent: Fri, Jan 27, 2012 8:17 pm Subject: Re: [meteorite-list] Etching solution Hi Doug, Thanks for the comments. I'm a Certified Industrial Hygienist and a Certified Safety Professional and have been in the chemical health and safety field for more years than I care to admit. Before that, I used to work as an analytical chemist. There is a lot of information you have passed on to the list with good intent, but there are several assumptions that you are making that are not substantiated. However, I agree that the purpose of the list is not to get into a deep discussion of health and safety issues. Anyone who would like to do so can contact me off-list. But I do have a concern that many of the comments in the threads have been a bit too casual - that may be my interpretation or reading only - and if so I apologize. But we have identified three unfortunate experiences with nitric acid/ethanol since the discussion started - and I want to do my best to warn those of the potential hazards that are involved before someone gets hurt or has another unfortunate tale to post on the internet. I think we all have the same objective as far as that goes. One last item - you may want to calculate the percent composition of the 3 molar (normal) solution you are recommending and compare the figure to Bretherick's data for instability. Mark Mark Grossman Meteorite Manuscripts ----- Original Message ----- From: "MexicoDoug" <mexicodoug at aim.com> To: <markig at westnet.com>; <Meteorite-list at meteoritecentral.com> Sent: Friday, January 27, 2012 7:46 PM Subject: Re: [meteorite-list] Etching solution Hi Mark, "Would appreciate a reference for the nickel chloride being 15 times more carcinogenic than soluble nickel nitrate." That's not what I wrote although it could be true I have no such reference to support the above. What I did write was: "Only Nickel chloride (a result of ferric chloride etching) is carcinogenic at levels 15 times lower than those produced from nitric acid etching." There is a huge difference between what you understood and what I actually wrote as threshhold toxicity levels don't necessarily equate to activity factors. This is because the body has dozens of competing homeostatic (metabolic, immune/allergic, etc.) processes that relate to detoxification and an imbalance occurs when that one single straw to many put on the camel breaks its back. The reference should be any MSDS (Material Safety Data Sheet), just check whichever one you have access to or dig up first. Toxicology, especially when it comes to carcinogens is so complex that I don't think anyone understands it, or they would already gotten a billion buck grant from the NIH by now. It just comes in many small pieces. I share your opinion that we should reference and I'm sorry if I just dumped all this information for discussion, but it was more useful that keeping i to myself. I've not found a reasonable layman's treatise anywhere on the subject so I figured the met list was as good as it gets without opening yet another research project to compete with the other ones I've got floundering. Anyway, the exposure limits I mention I believe are for lab rats approximating other mammals, like humans. Again, the more you get into this the more it's hard to muzzle oneself becasue now we're getting further into it: so - must ask, can you breath it in (probably not in most cases, but definiely cover your mouth, eyes, and any other open oriface such as a wound when doing this. That should be 'common knowledge' but really if doing it for the first time, maybe not. and - must ask, so how permeable is the skin to it ... becasue if one has a 15X lower threshhold but is 15x more difficult to uptake, then we'd have a wash. Then there are solubility issues, but these both look like they are well soluble, just a glance at the MSDS will answer that. last here, but definitely not any closure, is; what's the significance of getting these things into ones local envoironment and the general environment (waters, soils, air, etc.). We don't think about this but doing it out on the concrete patio outside of the kitchen and tossing the waste into the immediate area, it will dry and become particulate contaminants which over time the wind will distribute in the lungs of little boys playing there, through the kitchen window, etc. Probably no big deal in most cases, but there is always that one case that something goes terribly wrong. And getting back to the maximum 'permissible' exposure limit (sheesh, now to add residence time, cumulative properties in the body, it's head spinning). Which is why, in this case for a rat which is assumed to react as a human (but may not), at least we can point a finger at the threshold of toxicity, which itself is a a single point determined after half of the subjects have croaked, illustrating that half are just fine whereas it is toxic to half of them at even lower levels, or something along tose lines. As for your other reference of isopropyl vs. ethyl alcohols and explosion hazards, I'm sorry but perhaps someone else has more time to develop this properly vs. this informal discussion forum. If I had time and a full lab, I would start by maing a ternary diagram of the two alcohols and nitric acid, and plot the flash point of the mixture for starters. The information I saw was anecdotal and not rigorous nor very quantitative. However I don't hacve time to spend on this subject any more due to personal circumstances and recommend that you try googling. This is not a case of a proving beyond a reasonable doubt that it is more explosive. However there are enough warnings out there thaty would seem to suggest more violent and higher incidence of isopropanol-HNO3 mixtures than the EtOH analog, since we are talking about personal safety. Clearly Isopropyl alcohol is similar inproperties relating to etching that given the more widespread use in general metallurgy of EtOH, it's the devil we know better I'm convinced of the Isopropanol/ethanol issue all I need to be more vigilant. But that doesn't mean I wouldn't use it if there was some reason to do that. Rather than obsessing too much over a terribly complex issue and coming to the same inconclusion, I'd just make simple, yet effective modifications to my procedure - Why deal with comncentrated nitric in a home environment at all? How silly! You (general) want to save a few pennies at your own risk, pennywise --- just have the Hazardous Materials emergency number handy. Otherwise buy the diluted acid= problem significantly minimized. You want to make etchant? Don't make such a large amount in a bottle/beaker at once. Don't use such an excess when etching, experiment by painting it on with a brush instead - problem significantly minimuzed ... and so on. Hope this gives better insight. Having THE answer to these things is too tall an order, yet experience and common sense are why other individuals can etch more easily than making scrambled eggs. Our appreciation of risk is terribly distorted. Once I was in a discussion with Sterling sopmewhere discussing this and he even referenced someplace, proabbly wiki the bias I described had a name. You know, the same one that evaluates whether to be frightened from falling asteroids vs. driving to work in the morning. I'm still waiting for the thriller movie, "Highway jaunt" where no rogue asteroids or murderous psychopats pass by, but Strawberry Shortcake girl just takes her car for a spin and suddenly every individual in the traffic stream has a compulsion to run over her on her sweet bicycle. Point of the dumb example being the high risk we have experience has much lower fear factor than the almost non-existent risk which ends in carnage and mahem, even if a decision tree analysis shows that the friendly risk is a million times more likely. Kindest wsihes Doug PS I have stretched too much to participate in this give some other difficult responsibilities I ahve at the m,oment so I did my best and will likely retire for a while to catch up on things. PPS, After all this, I think my new etchant of choice will be Coca Cola. No doubt it works or can be tweaked to, too. -----Original Message----- From: Mark Grossman <markig at westnet.com> To: nf114ec <nf114ec at npgcable.com>; meteorite-list <meteorite-list at meteoritecentral.com>; MexicoDoug <mexicodoug at aim.com> Sent: Fri, Jan 27, 2012 6:20 pm Subject: Re: [meteorite-list] Etching solution Hi, Couple of thoughts. Mark's Law: If you're standing in the exact same spot as someone else when a mixture of nitric acid and ethanol explodes, the sensitivities of the two individuals to harm are always the same. :-) Both nickel chloride and nickel nitrate are soluble nickel compounds, and as far as carcinogenicity goes, the American Conference of Governmental Industrial Hygienists and the International Agency for Research on Cancer group the two compounds together. As far as I am aware, there was no singling out of nickel chloride as being 15 times more carcinogenic than nickel nitrate - you indicated both are products of etching - one from ferric chloride and the other from nitric acid. The insoluble oxides of nickel are more carcinogenic, but that's not the compounds you are referring to. Would appreciate a reference for the nickel chloride being 15 times more carcinogenic than soluble nickel nitrate. Similarly, would appreciate a reference to isopropyl alcohol being more dangerous to use for etching with nitric acid than ethanol, under the same set of conditions. Why is isopropyl alcohol more prone to a "freak" explosion or "blow up" than ethanol? Explosions with concentrated nitric acid and ethanol are well-documented. Now I am not relying on Wikipedia as an academic reference, but I think the information contained on the webpage is worthy of discussion and/or criticism. See http://en.wikipedia.org/wiki/Nital and the mention of the hazards associated with 5 and 10 percent solutions. This information appears to come from Bretherick, which is a pretty good chemical reference that I have used in the past (see http://www.ab.ust.hk/hseo/tips/ls/ls005.htm). Reading Material Safety Data Sheets should always be required - but realize that many are inadequate and often do not list or spell out the safety precautions which should be employed. A lot of technical information was contained in the last few emails, and if we all agree that respect for chemicals is critical, then it would be useful to confirm the facts. Thanks! Mark Mark Grossman Meteorite Manuscripts ----- Original Message ----- From: "MexicoDoug" <mexicodoug at aim.com> To: <nf114ec at npgcable.com>; <meteorite-list at meteoritecentral.com> Sent: Friday, January 27, 2012 1:02 PM Subject: Re: [meteorite-list] Etching solution > Hi Jim, > > My respects to all the ferric chloride lovers out there and especially Ron > Hartman, bless him. A blanket statement of a "better etch" is pretty > meaningless. I recall asking Arcady who had all the Seymchan several > years back why all of his specimens were etched so deeply that they looked > like someone chiseled the etch into them and then put on a matte > clearcoat. He said, the customers prefer a deep etch. I thought it was > butt ugly (not to mention a more discrete etching such as by mild nitric > acid's slow action introduces far less nucleation sites for oxidation). > There are so many factors. > > If the iron chloride etch were better it wouldn't hurt to send those > conclusions to the Smithsonian, British Museum, Weiner Naturhistorisches > Museum, Max-Planck-Institut f?r Chemie (or whatever its called now) > Collection, Paris Mus?um National d'Histoire Naturelle, etc. for comment. > ;-) > > BTW, there are many variables not realated to the etch to consider. > Though ferric chloride is 'easier', when it comes to mixing up, it doesn't > mean it is less toxic in other ways. Ever wonder if it was legal or smart > to pour spent solution down the drain or into the soils? Nickel chloride > and nickel nitrate (produced in etching) are both mutagenic. Only Nickel > chloride (a result of ferric chloride etching) is carcinogenic at levels > 15 times lower than those produced from nitric acid etching. But with all > the other heavy metal ions in iron meteorites, again, respect for the > chemical is important regardless of what risks are perceived - it's never > the full story and like smoking, everyone doesn't even have equal > sensitivity. > > Kindest wishes > Douh > > > -----Original Message----- > From: Jim Wooddell <nf114ec at npgcable.com> > To: Meteorite-List <meteorite-list at meteoritecentral.com> > Sent: Fri, Jan 27, 2012 6:48 am > Subject: Re: [meteorite-list] Etching solution > > > I believe there was an article by Hartman a few years back about the use > of > ferric chloride. The conclusion was that it gave a better etch??? I > think > it was in Meteorite-Times. > > Jim > > > > Jim Wooddell > http://k7wfr > > ----- Original Message ----- > From: "MexicoDoug" <mexicodoug at aim.com> > To: <mexicodoug at aim.com>; <markig at westnet.com>; > <meteoritesnorth at hotmail.ca>; <meteorite-list at meteoritecentral.com> > Sent: Friday, January 27, 2012 1:49 AM > Subject: Re: [meteorite-list] Etching solution > > >> "Besides water, I'm suspecting Nitric + acetone (Nitkeytone ?) and > any >> number of other solvents would work" >> >> OK, don'rt bother with this one! I just did; It actually etches, but >> leaves a yucky finish. The fumes are no worse than other nitals, > though I >> wouldn't want to breath much of them until I knew more; but there > didn't >> seem to be any decomposition. I used reagent grade acetone to avoid >> possibly nasty impurities, and the nitric acid concentration only > 3.9% >> just in case I hit a flash point, full face shield and a fan venting > right >> out the door. Nice to have had an 81 F day today and still its warm >> enough to open the door ;-) nice etch, terrible residue. >> >> Kindest wishes >> Doug >> >> >> >> -----Original Message----- >> From: MexicoDoug <mexicodoug at aim.com> >> To: markig <markig at westnet.com>; meteoritesnorth >> <meteoritesnorth at hotmail.ca>; meteorite-list >> <meteorite-list at meteoritecentral.com> >> Sent: Fri, Jan 27, 2012 3:11 am >> Subject: Re: [meteorite-list] Etching solution >> >> >> "explosive" >> >> Definitely caution when playing around with corrosives is of the first >> order...that said, >> >> sure, ethanol is a racing car engine fuel and under the right >> conditions can combust; But people drink it even straight... >> >> Many things we do have risks associated with them some very serious > and >> definitely we must respect all reagents especially corrosives like >> nitric acid. For example, many people enjoy fireworks. Yet, > fireworks >> are explosive and dangerous if you put them near sparks or heat,or try >> to light them with a charcoal grill. And obviously gasoline combusts >> too yet mechanics and Dads everywhere use it to clean hands and metal >> parts and also have arc welders nearby. Or sulfuric acid inside a car >> battery - don't get it on your bikini when working on the car! If you >> are going to use anything, it needs to be done with respect and a > quick >> read of the MSDS of whatever chemicals you are using... (and don't >> trust everything you read on a discussion l;ist posted at 3 AM) >> >> It is not a good idea to have concentrated nitric acid and ignore the >> label, for example and my heart goes out to Anita on that. Depends > the >> kind of person you are. When I make my smoothie in the morning I use >> fresh cherries as one of 18-20 ingredients and a preparation that > takes >> an hour. It's life threatening if I accidentally put a pit in my >> blender (which can easily liquify meteorites, it's so powerful) due to >> the specialized needs of a family member who cannot eat. So I double >> count the cherries first, count the pits as I punch them out, and then >> count them once again when I dispose of them. No shortcuts, All > common >> sense! >> >> Bart Simpson's pet python once made nital in an episode of The >> Simpsons, which is amusing if you haven't had a bad experience you >> can't laugh about.... I think the writers were Caltech rejects that > had >> to go to MIT and have to do this to humor themselves, this wasn't the >> only snarky chemistry episode. >> >> (episode: Stop or my Dog will Shoot!) >> >> Here's the link: >> >> http://video.i.ua/user/810302/8185/35583/ >> >> it take a little time to stream, but once ready the scene is at the >> 17:49 minute:seconds mark. >> >> ... and that' why in my summary which I did much too quickly to be >> complete, I suggest that you use water, that is to say, NitH20,. or as >> it's commonly known just dilute Nitric Acid, rather tha alcohols to >> develop your method. Nothing wrong with water, it is really getting a >> bum wrap and it is GRAS ;-) It is what everyone that is using FeCl3 > is >> using as a diluent, too. For the HNO3 the 3.0 N concentration works >> best for me. Absolutely no need to buy concentrated acid and you can >> avoid all the issues of what to add to what and no need for Hazmet >> backup. You can buy it already diluted, get the same benefit of a >> nitric acid etch (alcohol doesn't etch, it's only a carrier and >> diluent). Just crank up the oven to the higher end of a safe drying >> temperature. That's the only real benefit of alcohol in my opinion - >> it allows a cooler drying which can povide a nicer (lower oxdation >> residue on the virgin etched surface, but now we are staerting rally > to >> split hairs...IMO. >> >> Speaking of diluents, there's no reason nital (alcohol) is special as > a >> diluent. Besides water, I'm suspecting Nitric + acetone (Nitkeytone > ?) >> and any number of other solvents would work fine if not be hiding a >> secret for even a better etching solution. Sure acetone is flammable >> and can give you the willies too, you can't win but that doesn't stop >> women who understand the chemical they use from putting it on their >> fingernails ;-) granted not with acid, though I bet some do >> inadvertantly mix it with salycilic acid solution when disolving > excess >> skin ;-), which if not used properly could chemically remove a lot of >> flesh ... >> Kindest wishes >> Doug >> >> >> -----Original Message----- >> From: Mark Grossman <markig at westnet.com> >> To: MexicoDoug <MexicoDoug at aim.com>; meteoritesnorth >> <meteoritesnorth at hotmail.ca>; meteorite-list >> <meteorite-list at meteoritecentral.com> >> Sent: Fri, Jan 27, 2012 12:32 am >> Subject: Fw: [meteorite-list] Etching solution >> >> >> Did a quick search on the internet. Read this tale from the Meteorite >> Association of Georgia regarding the hazards of mixing nitric acid and >> ethanol: >> http://www.meteoriteassociationofgeorgia.org/article-052007.htm. >> >> Mark >> >> Mark Grossman >> Meteorite Manuscripts >> >> >> ----- Original Message ----- >> From: "Mark Grossman" <markig at westnet.com> >> To: <mexicodoug at aim.com>; <meteoritesnorth at hotmail.ca>; >> <Meteorite-list at meteoritecentral.com> >> Sent: Thursday, January 26, 2012 11:40 PM >> Subject: Re: [meteorite-list] Etching solution >> >> >>>I don't know all of the details of the etching process, but a word of >>>caution - mixing concentrated nitric acid with ethanol can result in >> an >>>explosion and a fire. I've witnessed the results of the reaction when >>>someone inadvertently mixed the two in a lab years ago. >>> >>> Mark >>> >>> Mark Grossman >>> Meteorite Manuscripts >>> >>> ----- Original Message ----- >>> From: "MexicoDoug" <mexicodoug at aim.com> >>> To: <mexicodoug at aim.com>; <meteoritesnorth at hotmail.ca>; >>> <Meteorite-list at meteoritecentral.com> >>> Sent: Thursday, January 26, 2012 11:23 PM >>> Subject: Re: [meteorite-list] Etching solution >>> >>> >>>> PS - if you don't have a hood or other exhaust, the methyl alcohol >> could >>>> also be dangerous becasue the liver breaks it down into toxins and >> you >>>> will inhale some of it. That's another reason why I use ethanol in >> the >>>> oven, and frankly much more important a reason than saving a few >> pennies >>>> ;-) You can consider the residence time of the toxins in your >> system to >>>> be as long as a week, so if your are doing etxching all day long,and >> are >>>> using methanol nital you definitely need a very well ventilated >> place, >>>> and methanol is sneaky worthy of a CSI episode of an innocent who >> done it >>>> since the syptoms and critical second hit can be stealth and barely >>>> naseaous for the first. >>>> >>>> I know you didn't ask about methyl alcohol, but its good to see the >> 4 >>>> common solcvent benefits/liabilities side by side, at least my take >> on >>>> it. Anyway, you can see why ethyl alcohol iis usually preferred. I >> just >>>> checkethe azeotrophes andisopropyl is only 2.3 C above ethanol >> mixtures >>>> so its ability to remove water would be very similar in the oven, >> the >>>> last thing to look up to decide theoretically approximating the >>>> penetrating ability as related to the surface tension of the alcohol >>>> (just a guess) what is the bestest alcohol would be to check the >> surface >>>> tension. I just did and all three alcohols are nearly 4 times that >> of >>>> water and within 5% o each other, so I would think that on >> penetrating >>>> ability they are probably all tied and would argue all factors >> considered >>>> ethanol is best since the worst you get is a standard hangover in >>>> standard use conditions, and to get a freak explosion from EtOH >> mixtures >>>> with acid is minimal compared to isopropyl. >>>> >>>> Ferric chloride of course doesn't have the toxicity not >> flammability, but >>>> it stains like heck and with proper respect for the reagents plus a >>>> little experience, like everything else the risks are minimized. >> That's >>>> another reason to start with dilute nitric which I highly recommend >> until >>>> you have the bugs worked out of the etching "assembly line", ie, >> method >>>> you find best for your work. >>>> >>>> Good luck, >>>> >>>> Kindest wshes >>>> Doug. >>>> >>>> >>>> -----Original Message----- >>>> From: MexicoDoug <mexicodoug at aim.com> >>>> To: meteoritesnorth <meteoritesnorth at hotmail.ca>; Meteorite-list >>>> <Meteorite-list at meteoritecentral.com> >>>> Sent: Thu, Jan 26, 2012 10:30 pm >>>> Subject: Re: [meteorite-list] Etching solution >>>> >>>> >>>> Craig, >>>> Let me add (the message actually got away before being finished as I >>>> write piecemeal and then send) that as far as etching it works fine, >>>> but if you look at the series of alcohols, methyl (bp = 65 C), ethyl >>>> (bp = 78 C) and isoproply alcohol (bp = 83 C), methyl alcohol >>>> (methanol) is by far the safest until you get a lot of experience >>>> working with these under a hood. "Ethyl nital" is mildly flammable >> in >>>> and Isopropyl nital is pretty dangerous since if can blow up in >> certain >>>> conditions that aren't difficult to arrange. Nothing to do with the >>>> etching results which are left to trial and error, but rather the >>>> safety which I should have mentioned. >>>> >>>> While all the alcohols work fine, keep in mind two of the factors > you >>>> are working with are miscibility/penetrant ability and vapor >> pressure. >>>> Vapor pressure you can estimate by boiling point - lower bp is a >> higher >>>> vp. The higher vp the quicker it will evaporate out, so methanol >> would >>>> seem to have the advantage, thought it might form some azeotropes > and >>>> stay in longer, as could the rest without looking this up (no time > at >>>> the moment). >>>> >>>> To the series of three common alcohols you could just add water bp = >>>> 100 and consider it almost as a continuim and play with the you like >>>> which will influence drying time among other important parameters. > I >>>> use methanol and later rinse with ethanol (cheaper for me), which is >>>> the reverse of good drying practice I would think, but half of the >> time >>>> I just use the diluted acid at 2 - 3 N. >>>> >>>> Hope that was a better answer, sorry for not finishing the first >>>> kindest wishes >>>> Doug >>>> >>>> >>>> -----Original Message----- >>>> From: Craig Moody <meteoritesnorth at hotmail.ca> >>>> To: mexicodoug <mexicodoug at aim.com> >>>> Sent: Thu, Jan 26, 2012 9:42 pm >>>> Subject: RE: [meteorite-list] Etching solution >>>> >>>> >>>> Much appreciated Doug, Thank you! I have lots of 99% around. >>>> >>>> Craig >>>> ______________________________________________ >>>> >>>> Visit the Archives at >>>> http://www.meteoritecentral.com/mailing-list-archives.html >>>> Meteorite-list mailing list >>>> Meteorite-list at meteoritecentral.com >>>> http://six.pairlist.net/mailman/listinfo/meteorite-list >>>> >>>> ______________________________________________ >>>> >>>> Visit the Archives at >>>> http://www.meteoritecentral.com/mailing-list-archives.html >>>> Meteorite-list mailing list >>>> Meteorite-list at meteoritecentral.com >>>> http://six.pairlist.net/mailman/listinfo/meteorite-list >>> >>> ______________________________________________ >>> >>> Visit the Archives at >>> http://www.meteoritecentral.com/mailing-list-archives.html >>> Meteorite-list mailing list >>> Meteorite-list at meteoritecentral.com >>> http://six.pairlist.net/mailman/listinfo/meteorite-list >> >> >> ______________________________________________ >> >> Visit the Archives at >> http://www.meteoritecentral.com/mailing-list-archives.html >> Meteorite-list mailing list >> Meteorite-list at meteoritecentral.com >> http://six.pairlist.net/mailman/listinfo/meteorite-list >> >> ______________________________________________ >> >> Visit the Archives at >> http://www.meteoritecentral.com/mailing-list-archives.html >> Meteorite-list mailing list >> Meteorite-list at meteoritecentral.com >> http://six.pairlist.net/mailman/listinfo/meteorite-list > > ______________________________________________ > > Visit the Archives at > http://www.meteoritecentral.com/mailing-list-archives.html > Meteorite-list mailing list > Meteorite-list at meteoritecentral.com > http://six.pairlist.net/mailman/listinfo/meteorite-list > > ______________________________________________ > > Visit the Archives at > http://www.meteoritecentral.com/mailing-list-archives.html > Meteorite-list mailing list > Meteorite-list at meteoritecentral.com > http://six.pairlist.net/mailman/listinfo/meteorite-list > Received on Sat 28 Jan 2012 12:18:27 AM PST |
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